Critical Exposure Pathways

1. Workshop #13 Critical Exposure Pathways October 17, 2007 Elizabeth Callahan, MassDEP John Fitzgerald, MassDEP

2. 7:00 – 7:40 CEP Concepts & Process (EC) Q&A 7:40 – 8:30 Vapor Intrusion Pathway (JF) Q&A 8:30 – 8:40 BREAK 8:40 –9:20 Regulatory Guidelines & Rules of Thumb (EC) Q&A 9:20- 10:00 Technical Guidelines & Rules of Thumb (JF) Q&A Workshop Overview

3. CEP Concepts & Process

4. (a)vapor-phase emissions of measurable concentrations of OHMs into the living or working space of a pre‑school, daycare, school or occupied residential dwelling; OR CEP Definition – 40.0006 Critical Exposure Pathways mean those routes by which OHM(s) released at a disposal site are transported, or are likely to be transported, to human receptors via:

5. CEP Definition – 40.0006 (cont.) (b) ingestion, dermal absorption or inhalation of measurable concentrations of OHMs from drinking water supply wells located at and servicing a pre‑school, daycare, school or occupied residential dwelling.

6. Risk and Required Mitigation • must promptly eliminate Imminent Hazard CEP No Substantial Hazard • must achieve for a Temporary Solution • must eliminate, mitigate or prevent pathway, to the extent feasible Risk No Significant Risk • must eventually achieve for a Permanent Solution No Risk

7. Why Do We Care about CEPs? • CEPs address Exposure Pathways in schools, day cares, and homes, where frequency of exposure is likely high • Uncertainties in chemical toxicity information and risk characterization • Sensitive populations (e.g., infants, children, fetal development, compromised immune systems)

8. Statutory Basis - CEP Section 3A(g) Chapter 21E Permanent Solution Requirements • Achievement of “No Significant Risk” (HI, ELCR) • Where feasible, a permanent solutions shall include measures to reduce to the extent possible the level of OHM to the level that would exist in the absence of the disposal site (i.e., “background”)

9. Statutory Basis - Feasibility Section 3A(h) Feasibility Criteria • No technology exists • Costs outweigh the benefits • Expertise not available • No available disposal location

10. Regulatory Requirements –IRAs and CEPs • 40.0414(3) – IRAs are presumed to require the elimination and/or mitigation of CEPs • 40.414(4) IRAs are presumed to require the prevention and/or mitigation of CEPs These are REBUTTABLE PRESUMPTIONS, based on feasibility

11. Condition of Substantial Release Migration (SRM) - 40.0006 a condition at a disposal site that includes any of the following:… (d) releases to groundwater that have been or are within one year likely to be detected in a public or private water supply well; … (f) releases to groundwater or to the vadose zone that have or are within one year likely to result in the discharge of vapors into school buildings or occupied residential dwellings.

12. SRM Condition - Notification • 72 hour notification condition* • Requires an IRA * where such condition is associated with a release for which notification otherwise is or has at any time in the past been required (40.0313(5))

13. Life Cycle of a CEP *Action presumed, unless measures are not feasible and no IH exists or is likely to exist IRAC No IRA Action No Action not feasible not feasible Phase III Feasibility Evaluation Conduct IRA* Condition Feasibility Evaluation Notify IRA cont’d no Action Phase IV /V/ROS feasible feasible Condition** addressed? IRA Action ** without continued operation of an Active Remedial System IRAC yes

14. CEP • Expedites consideration of cost-effective measures to eliminate, reduce or prevent exposures in schools, day cares and homes from vapors or drinking water • Front loads the background feasibility evaluation into the IRA where a Critical Exposure Pathway exists

15. MCP Feasibility Evaluations – 40.0860 • Selection of Remedial Alternatives • Permanent Versus Temporary Solutions • Reducing OHM below UCLs • Critical Exposure Pathways • Technologies that Reuse, Recycle, or Treat OHM • Achieving or Approaching Background

16. OHM concentration OHM toxicity OHM persistence Uncertainty in site characterization, complexity of site conditions Cost of mitigation alternatives Effectiveness of mitigation alternatives Timing Feasibility Considerations

17. Cost Feasibility Considerations Critical Exposure Pathways Benefit @ conc 100

18. Feasibility Considerations Critical Exposure Pathways Benefit @ conc 1 Cost

19. Conceptual Site Model

20. Vapor Intrusion Phenomenon • P

21. Building Depressurization Stack Effects Wind Exhaust Fans • P to 50 Pa Strongest 3-6‘ Furnace combustion Up to 20-25’

22. Winter windows closed… Less fresh air infiltration frost layer

23. (Water) Vapor Intrusion Dry Soils?

24. Moisture Considerations Basement Slab

25. MassDEP Site Data- Subslab soil samples 0.06

26. Fresh Water Lens well Infiltration fresh water lens groundwater flow VOC plume

27. Lines of Evidence Approach

28. Lines of Evidence PID Screening Cracks/Annular Spaces/Floor Drains Typical Indoor Air Conc. Basement vs. upper floors Modeling Chemical Forensics Indoor Air Data Sub Slab Soil Gas Conc GW concentration

29. Groundwater Conc vs GW-2 Std Type Contaminant Distances Depth Petro Chlorinated VOCs Freshwater Lens 300’ – 500’ Ethanol Effects?

30. Sub-Slab Soil Gas Data – Typical Observations Chlorinated VOCs 10 – 100X Dilution Petro: 100 – 1000X Dilution

31. Indoor Air Data > Published Values? Typical Indoor Air Conc. Use of Chemicals in Building? Basement vs. upper floors Should be higher in lower level(s) unless HVAC Issues MtBE – Usually not from GW Chemical Forensics Petro – Check Chromatograms Chlorinated VOCs – Degradation Products? Cis 1,2-DCE?

32. Mitigation

33. Hierarchy Seal Cracks/Spaces & Earthen Floor Seal/Vent Sumps; Seal/modify floor drains HVAC/Heating System Modifications Sub-Slab Depressurization System Overpressurization Systems

34. SSDS

35. Less Uncertainty Typical Costs $ Benefit Benefit < $5K Feasibility of Vapor Intrusion Pathway Elimination

36. Drinking Water Wells Two Flavors…..

37. Private Water Supply Wells Defined in 40.0006 of MCP: < 15 Service Connections; or < 25 People for 60 Days FOR HUMAN CONSUMPTION (i.e., not irrigation well)

38. Public Water Supply Wells Defined 40.0006 via 310 CMR 22.02: >15 Connections or Servicing >25 Individuals for at least 60 days/year Community: Municipal/District Systems Non Community: Restaurants, Camps, Golf Courses, Apartments, Schools

39. Critical Exposure Pathway Private Wells Non-Community Public Supplies Residential School Residential (on-site well) POTABLE water

40. Not All CEPs are Reportable…. CEPs are a sub-universe of Conditions of Substantial Release Migration (SRM) SRMs require reporting ONLY when associated with a Release that is otherwise Reportable

41. Not Reportable Gas MtBE @ 9 g/L Unknown Source Reportable SRM/CEP > RC

42. MtBE @ 79 g/L Reportable SRM/CEP Unknown Source

43. Mitigation Drinking Water Treatment Systems High VOCs (Showering/Dermal) Lower Level VOCs Low to Moderate MtBE Lower Metals Point of Entry Point of Use

44. Mitigation Drinking Water Treatment Systems Metals Perchlorate VOCs VOCs Petroleum Air Stripping Activated Carbon Reverse Osmosis

45. Mitigation Drinking Water Treatment Systems Problem Contaminants (Cost/Benefit Issue): MtBE Ethanol

46. Less Uncertainty Typical Costs $ Benefit Benefit < $5K Feasibility of Drinking Water Pathway Elimination

47. Regulatory Guidelines & Rules of Thumb 

48. When to be Concerned about a Possible Vapor Intrusion Pathway • Site conditions, events • Complaints of odors • Saturated soils, NAPL beneath or immediately adjacent to the structure • Groundwater concentrations > GW-2 standards within 30 feet of building foundation, groundwater depth 15 feet or less

49. Groundwater Concentrations < GW-2 Generally, further investigation of indoor air pathway and CEP issues is not warranted Exceptions • Odors, OHM likely attributable to groundwater contamination observed in structure • Earthen floor, field stone foundation, and/or groundwater sumps with COC chlorinated contaminants • NAPL/saturated soils within 30 feet of structure

50. When to be Concerned About a Possible Drinking Water Well Impact • Groundwater OHM plume proximate (500 feet) to a water supply well that serves a school, day care, or residence • Potential migration in bedrock to well • MtBE or chlorinated contaminants